Indicator tube with electrodes supported by a rigid insulating mass



Apnl 21, 1970 r A. B. SHESSER 3,508,102

. INDICATOR TUBE WITH ELECTRODES SUPPORTED BY A RIGID INSULATING MASSFiled April 30. 1968 FIG.Z

INVE/WDR. ARTHUR B. SHESSER BY M4 aw ATTORNEY United States Patent US.Cl. 313-1095 6 Claims ABSTRACT OF THE DISCLOSURE The disclosure is of acold cathode, gas-filled indicator tube which has an envelope of minimaldiameter and length and includes a stack of cathode electrodes in theform of characters which face the side wall of the envelope. Theenvelope includes a flat base and a flat dome which lie close to theupper and lower ends of the cathode electrodes. Support for the upperend of the electrode assembly may be provided in diiferent ways, and, atthe lower end, tube pins support the anode and cathodes. In addition,the cathode leads and the tube pins to which they are connected areembedded in a mass of insulating material which serves to shield thecathode leads and the tube pins and to provide a rigid support for thelower ends of the cathode characters. The mass of insulating material isshaped to prevent the deposition of continuous paths of sputteredcathode metal between adjacent cathode characters.

BACKGROUND OF THE INVENTION Indicator tubes of the general typedescribed above have been manufactured successfully and have been usedcommercially for many years. However, there is an everpresent need tominiaturize, eliminate parts, and reduce the cost of manufacture ofthese tubes.

SUMMARY OF THE INVENTION Briefly, a display tube embodying the inventionincludes a gas-filled envelope having a base and dome including anelectrode assembly which occupies substantially the entire volume of theenvelope. The base of the envelope carries tube pins to which the anodeand cathode mounting tabs are secured, and, in addition, the cathodemounting tabs and their tube pins are embedded in a mass of insulatingmaterial as part of the support therefor. This permits a minimum numberof auxiliary support elements to be employed. The insulating material isshaped to prevent the formation of continuous conducting paths betweencathodes as may be formed by sputtering of the cathode material duringmanufacture or operation.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a perspective view of a tube embodying the invention;

FIG. 2 is a front elevational view, partly in section, of the baseportion of the tube of FIG. 1; and

FIG. 3 is a side elevational view of the stem portion of the tube ofFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An indicator tube embodying theinvention includes an envelope 20 which contains a gas suitable forsupporting cathode glow. Such a gas may be argon, neon, or the like, ata pressure which may be in the range of about 30 to about 100 mm. ofmercury. If desired, other substances such as mercury may be added insmall quantities to the gas content of the envelope.

3,508,102 Patented Apr. 21, 1970 The envelope 20 is generally elongatedand its side wall 30 comprises a viewing window through which glowingcathodes may be viewed. The envelope 20 includes a base or stem 40,through Wich metal pins or leads extend, and by means of whichelectrical connection is made from the cathode character electrodeswithin the tube to external electrical circuitry. For maximumutilization of space, the pins of leads 50 are oriented in two rowsparallel to a diameter of the stern as shown. However, it is clear thatthese leads 50 may be oriented in a single row or in a circle or in anyother manner, if desired. Two or more auxiliary leads or pins areprovided in the stern for connection to the tube anode, and these pinsare provided with glass sleeves for shielding purposes, if this isdeemed necessary. Two other pins are provided for connection toauxiliary electrodes to be described.

The upper end of the envelope remote from the stem is known as the domeof the envelope and carries a tubulation for evacuating the envelope andfilling it with the desired gas atmosphere. Tubulation 110 could be atanother location on the tube envelope, if desired.

The electrode assembly of tube 10 includes a stack of cathode electrodeswhich are in the form of numerals, letters or other characters, and atubular anode electrode which surrounds and encloses the cathodeelectrodes. The anode electrode comprises a solid back plate and a frontmesh screen which curve and meet each other at the sides of the cathodestack where they merely touch or are welded together. The pins 60* atthe rear of the stem are welded to the anode back plate 130 to providesupport and to serve as means for applying operating potential to theanode. A similar lead may also be secured to the screen 140, if desired.

The cathode electrodes 120 are of a metal such as stainless steel, andeach includes a main body portion, in the shape of a character, andupper and lower mounting leads or tabs and 160, respectively. The lowertabs extend downwardly from the main body portions of their cathodes sothat the come into direct alignment with leads 50, and each tab iswelded to a lead. Preferably, the tabs 160 of adjacent cathodes in thestack are welded to pins in difierent rows to maximize the spacingbetween them.

The upper cathode tabs 150 may be supported in different ways. In onearrangement, a support post is secured between the rear plate 130 andfront screen 140 by means of eyelets or by welding or the like, and thecathode tabs 150 are mounted thereon by means of suitable apertures orslots in the tabs, and they are insulated from each other by insulatingwashers 180. The post 170 is either made of an insulating material, orit is made of metal and coated or sleeved with glass, or the like. Theupper cathode tabs may also be supported in many other ways known in theprior art. For example, a box-like member (not shown) may be securedbetween the anode plate and screen, and the cathode tabs may be insertedinto the box through appropriate slots and held in place by aninsulating cement. Alternatively, if the cathodes are suflicientlystrong, they may not require an upper support.

In order to prevent the lower cathode tabs 1'60 and their pins 50 fromglowing during tube operation and to provide a rigid mountingarrangement and support therefor, these members are embedded in a mass200 of insulating material which extends from the top surface of thestem up to the lower edge of the character-shaped main body portion ofeach cathode 120. Sufiicient insulating material is used to embed thetabs and pins and to provide a solid, rigid mass which performs both theinsulating function and the function of supporting the cathodeelectrodes by supporting their lower tabs. One suitable material for theinsulating mass 200 is a mixture of chrome oxide and sodium silicatewhich adheres well to the metals normally used in such tubes. Othermaterials such as sauereisen, a mixture of aluminum oxide and potassiumsilicate, or various glass frits, might also be used.

Sometimes, during the processing or operation of tubes such as tube 10,metal is sputtered off by the cathode electrodes, and this metaldeposits on the cathode tabs and other supporting members. If acontinuous path of metal forms between two cathodes, then the cathodesare shorted and the tube is rendered useless. To prevent this fromhappening on the mass 200 which supports the lower cathode tabs, notches220 are formed in the mass between adjacent cathodes. These notches arepreferably deeper than they are wide to insure their performing thedesired function. The formation of paths of sputtered metal at the upperends of the cathodes is prevented by having the washers 180 on post 170between cathodes of a special shape to provide maximum surface, as iswell known in the art.

For optimum operation and long life, the tube includes in its atmospherea small quantity of mercury vapor which serves to minimize cathodesputtering during tube operation. The mercury may be provided in anysuitable fashion. For example, it may be introduced directly with theprimary gas atmosphere, or it may be released by heat from a capsule 230suitably located within the envelope.

The tube 10 also includes the auxiliary characters 90 such as decimalpoints or commas or the like which are located on both sides of thestack of cathodes at positions which such characters would normallyoccupy. Each auxiliary character arrangement includes a pin 80 providedwith a glass sleeve 70, and a ceramic washer 240 seated on the upper endof the glass sleeve 70. A metal disk 250 of cathode material, whichcomprises a decimal point, is positioned with its lower edge resting onthe washer 240 and is welded to pin 80.

What is claimed is:

1. A side-view cathode glow indicator tube comprising an elongatedenvelope containing a gaseous atmosphere capable of supporting cathodeglow, said envelope including an elongated viewing window parallel tothe principal axis of said envelope,

said envelope including a base at its lower end and a dome at its upperend having a tubulation,

an electrode assembly comprising cathode electrodes and an anodeelectrode mounted within said envelope facing said viewing window,

a plurality of first cathode tube pins extending through said base intosaid envelope for connection to said cathode electrodes and forconnecting said cathode electrodes to external electrical circuits,

other tube pins extending through said base into said envelope, at leastone of which is connected to said anode electrode,

said cathode electrodes comprising character-shaped electrodes assembledin a stack and arrayed in substantially parallel planes facing saidviewing window,

each cathode electrode including a character-shaped portion and at leastone cathode support at the lower end thereof, each said cathode supportbeing secured to one of said first tube pins so that the lower ends ofsaid cathodes are secured in place with respect to the base of the tube,

a rigid mass of insulating material enclosing said first tube pins andsaid lower cathode supports to which they are secured and extending fromthe surface of said base to the lower end of said character-shapedportion of said cathode electrodes whereby only the character-shapedportion of each cathode electrode is exposed to view, and

slots in said mass of insulating material between said cathodeelectrodes for preventing the formation of continuous paths of sputteredcathode metal between cathode electrodes.

2. The tube defined in claim 1 wherein said insulating materialcomprises a mixture of chrome oxide and sodium silicate.

3. The tube defined in claim 1 and including support means engaging andsupporting the upper ends of said cathode electrodes.

4. The tube defined in claim 1 and including support means engaging andsupporting the upper ends of said cathode electrodes, said support meanscomprising a post secured to said anode electrode and carryinginsulating members positioned between each of said cathode electrodes toinsulate them from each other.

5. The tube defined in claim 1 wherein said anode electrode comprises ananode plate positioned behind all of said cathode electrodes, and ananode screen positioned in front of all of said cathode electrodes, andincluding support means secured between said anode plate and anodescreen and engaging and supporting the upper ends of said cathodeelectrodes.

6. The tube defined in claim 5 wherein said insulating materialcomprises a mixture of chrome oxide and sodium silicate.

References Cited UNITED STATES PATENTS 3,358,176 12/1967 Rosenberg et al313-1095 3,437,861 4/1969 Koshizuka et al. 313109.5

RAYMOND F. HOSSFELD, Primary Examiner D. OREILLY, Assistant ExaminerU.S. Cl. X.R. 3l3266

